Investigators say 21-year-old Hector Baez is now charged with armed robbery and assault with attempt to murder.

According to sources he was picked up Thursday night at a South Boston housing development. Investigators say forensic evidence from the scene led them to Baez.

He will be arraigned Friday in Woburn District Court.

WBZ-TV’s Beth Germano reports

“This significant case development is a tribute to excellent collaborative police work and we are grateful to the Massachusetts State Police Crime Lab for their quick work in matching the defendant to forensic evidence that was gathered at the crime scene,” Middlesex District Attorney Gerry Leone said in a statement.

Gunfire erupted at a busy Woburn plaza on September 6 when officer Robert DeNapoli responded to a 911 call for an attempted armed robbery at Musto Jewelers. He was shot several times, leading police to search for as many as two or three suspects. One was arrested shortly after the shooting, 25-year-old Antonio Matos of Boston.

Antonio Matos holding a firearm at a gun range.

Matos was charged last week with two counts of masked armed robbery and two counts of assault with the intent to murder in connection with the incident. He remains hospitalized in serious condition and has yet to be arraigned.

Police say Matos and Baez, and possibly one or more others, planned and carried out the armed masked robbery at Musto Jewelers in which Woburn Police Officer DeNapoli was shot upon responding to the scene.

The investigation and search for additional suspects remains ongoing.

At Brothers Pizza, in the same plaza as the jewelry store, employee Harrison Carvalho said he was pleased with the progress in the case. “What can I say, we feel safer now,” he said. Remembering the grim day of the shooting he said everyone was nervous. “You think here it’s safe in Woburn. I never saw anything like this happen here,” he said.

Officer DeNapoli was released from the hospital last week and is recovering from his injuries.